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| United States Patent |
5,224,837
|
|
Lamphere
, et al.
|
July 6, 1993
|
Apparatus for recovery of liquid hydrocarbon
Abstract
A pump unit for recovery of hydrocarbon liquid from atop water in a well
includes a hydrocarbon pump intake with a linear probe for indicating the
position of the pump intake relative to the hydrocarbon/water interface on
a control panel, so that its relative position can be monitored and
changed. The probe has a conductive member coated with a non-conductive
coating, and is attached to a source of low frequency electrical signal.
The strength of a signal output from the probe indicates the position of
the probe, and the pump intake, relative to the hydrocarbon/water
interface and controls a display on a control panel. Furthermore, the
signal can be used to control the hydrocarbon/water interface relative to
the pump intake by such means as pumped water from under the pump intake
in a controlled manner to change said interface relative to the intake or
by means of a motorized lift to reposition said pump intake relative to
the interface.
| Inventors:
|
Lamphere; David A. (Westford, VT);
Bowles; David F. (Ferrisburg, VT)
|
| Assignee:
|
Clean Earth Technology, Inc. (North Ferrisburgh, VT)
|
| Appl. No.:
|
693956 |
| Filed:
|
April 29, 1991 |
| Current U.S. Class: |
417/63; 210/104; 417/37 |
| Intern'l Class: |
F04B 021/00 |
| Field of Search: |
417/63,36,37
210/104
|
References Cited
U.S. Patent Documents
| 4226714 | Oct., 1980 | Furness et al. | 210/104.
|
| 4273650 | Jun., 1981 | Solomon | 210/104.
|
| 4466777 | Aug., 1984 | Kimberlin | 417/63.
|
| 4469170 | Sep., 1984 | Farmer, Jr. | 166/53.
|
| 4663037 | May., 1987 | Breslin | 210/170.
|
| 4752188 | Jun., 1988 | Gurega | 417/36.
|
| 4916940 | Apr., 1990 | Mougne | 73/61.
|
Primary Examiner: Bertsch; Richard A.
Assistant Examiner: Freay; Charles G.
Attorney, Agent or Firm: Lahive & Cockfield
Claims
What is claimed is:
1. A pump unit for recovery of liquid hydrocarbon form a body of liquid
with a hydrocarbon/water interface, comprising
a pump with a pump intake, and
a linear probe, fixed in relation to said pump intake, and oriented to
extend perpendicularly to said hydrocarbon/water interface and through
said hydrocarbon/water interface, when in use,
said probe including antenna means for generating an electromagnetic signal
and electrical driving means for driving said antenna means, said driving
means including signalling means for generating a signal indicative of the
linear location of said hydrocarbon/water interface relative to said pump
intake, wherein said linear probe includes a linearly extending
electrically conductive member comprising said antenna means, a
non-conductive coating on said conductive member, and means for
electrically driving said conductive member with a low frequency
electrical signal.
2. The pump unit of claim 1 wherein said signalling means includes means
for generating a continuously varying signal indicative of the
continuously varying linear location of said hydrocarbon/water interface
relative to said pump intake.
3. The pump unit of claim 1 further including receiving means for receiving
said signal, and display means responsive to said signal for displaying
the relative location of said hydrocarbon/water interface relative to said
pump intake.
Description
FIELD OF THE INVENTION
This invention relates to apparatus and methods for the recovery of liquid
hydrocarbon based products (e.g., oil, gasoline, etc.) present in
groundwater through spills and leakage, and particularly to apparatus and
methods used with wells driven into the ground to facilitate such
recovery.
BACKGROUND OF THE INVENTION
One method for the recovery of liquid hydrocarbon present in the ground,
where it floats atop the groundwater, involves the drilling of a well to
below the water table. The method is described in U.S. Pat. No. 4,273,650
to Solomon, for example. A perforated well casing is inserted into the
well, and water and hydrocarbon seep into the well through the perforated
casing. By pumping water from the bottom of the well with a submersible
pump, a cone-shaped depression in the water table occurs with the well as
the center of the cone. The lighter hydrocarbon liquid collects in the
well on top of the water, and is removed by a second, hydrocarbon, pump
located at a fixed position near the liquid surface in the well.
The second pump has associated with it a point sensor that signals when the
water/hydrocarbon interface is high, where the pump shuts off so that it
will not pump out water instead of hydrocarbon. Another point sensor
signals when the water/hydrocarbon interface is low, so that the second
pump can operate, and pump out hydrocarbon.
Various improvements in this system have been suggested. Farmer, in U.S.
Pat. No. 4,469,170, discloses a floating pump and sensor assembly. The
floating assembly still includes only point sensors, so that the pump
operates when a lower sensor is activated by the water/hydrocarbon
interface, and shuts off when a higher sensor is activated by the rising
water/hydrocarbon interface. Breslin, in U.S. Pat. No. 4,663,037,
discloses a floating pump that relies on the specific gravity of the pump
to float at an appropriate depth near the water/hydrocarbon interface, and
has a hydrocarbon intake at the top of the pump, above the interface.
However, the optimum location of the intake of the hydrocarbon pump
relative to the hydrocarbon/water interface varies at different stages of
the operation of the system. When the depth of hydrocarbon above the water
interface is great, the hydrocarbon pump intake is preferably a
substantial distance above the interface, so that hydrocarbon instead of
water is more certainly pumped out. When the depth of hydrocarbon above
the water interface is shallow, the hydrocarbon pump inlet has to be very
close to the water interface so that it can still pump out hydrocarbon.
SUMMARY OF THE INVENTION
Accordingly, the invention provides a hydrocarbon pump unit for recovery of
liquid hydrocarbon from a body of liquid with a hydrocarbon/water
interface, comprising a pump with a pump intake, and a linear probe, fixed
in relation to the pump intake and oriented to extend perpendicularly to
the hydrocarbon/water interface when in use, the probe including
signalling means for generating a signal indicative of the linear location
of the hydrocarbon/water interface relative to the pump intake.
Preferably, the probe signalling means includes means for generating a
continuously varying signal indicative of the continuously varying linear
location of the interface relative to the pump intake. It preferably also
includes receiving means for receiving the signal, and display means
responsive to the signal for displaying the relative location of the
interface relative to the pump intake. Also, the linear probe may include
a linearly extending electrically conductive member, with a non-conductive
coating on the member, and means for exciting the conductive member with a
low frequency electrical signal.
The invention also comprises a method for recovering liquid hydrocarbon
from a well containing liquid hydrocarbon and water that define a
hydrocarbon/water interface, comprising the steps of locating a pump with
a pump intake above the hydrocarbon/water interface, determining the
linear position of the pump intake relative to the interface, operating
the pump when the pump intake is surrounded by hydrocarbon, and knowingly
varying the linear position of the pump relative to the interface to
maximize operation of the pump.
Preferably, the method further includes pumping water from the well to
change the location of the hydrocarbon/water interface, at varying rates
through a conduit controlled by a valve, the duty cycle of which varies
the water flow and thus raises or lowers the hydrocarbon/water interface
as desired, while maintaining near continuous operation of the water pump.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention will be described
or will be apparent from the following description of a preferred
embodiment of the invention, including the drawings thereof, of which:
FIG. 1 is a diagrammatic view of a system incorporating the invention,
utilizing a water depression mode of operation;
FIG. 2 is a side view of the hydrocarbon pump unit of the system, with
portions of the pump unit inlet screen broken away to show the interior of
the unit;
FIG. 3 is a view of a control panel for operating the system of the
invention;
FIG. 4 is a schematic diagram showing some of the electronic control
circuitry used in the system; and
FIG. 5 is a diagrammatic view of an alternative system utilizing an
automatic hydrocarbon pump positioning system.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown a well 10 drilled into the ground
12 in a location where the groundwater 14 has been contaminated by liquid
hydrocarbon 16 such as oil or gasoline. The contamination can result from
a spill above the ground or from seepage from an underground tank or pipe.
Since liquid hydrocarbon is lighter than water, it will accumulate above
the water in the water table 18.
The well 10 is drilled to a depth below the water table 18, and a well
casing 20 is inserted into the well cavity. The well casing 20 is
perforated so that liquid hydrocarbon 16 and water 14 from the surrounding
ground 12 can seep into the well 10. A hydrocarbon pump unit 22 is located
at the hydrocarbon/water interface 24 to pump out hydrocarbon 16. A
conventional submersible water pump 26 is located at the bottom of the
well 10 to pump out water, creating a depression 28 in the water table 18
centered at the well 10. The pumped out water 14 passes through a conduit
30 such as a pipe or hose, and through a flow meter 32, to treatment, such
as an aeration tower (not shown), and eventual return to the ground. In
the system shown in FIG. 1, the water also passes through a solenoid valve
34, which is electrically controlled to vary the volume of water passing
through the conduit 30. A control panel 36 with a graphic display (see
FIG. 3) is located at some above ground location where an operator can
monitor and operate the system. The flow meter 32, for example, sends a
signal through a connecting cable 31, to a display on the panel 36,
including both an indicator 33a of total gallons pumped and an array of
LED indicators 33b showing the rate of pumping.
Generally, there is some volume of flow of water from the submersible pump
26 that achieves an appropriate balance between lowering the water 14 in
the well 10 enough to draw more water and hydrocarbon pump into the well,
but not so much that the hydrocarbon pump unit 22 for drawing off
hydrocarbon 16 above the water 14 is rendered ineffective. An electronic
flow control circuit 38 in the panel 36 compares the desired position of
the hydrocarbon pump 22 relative to the hydrocarbon/water interface 24 and
varies the duty cycle of the solenoid valve 34 accordingly (see FIG. 4). A
control lever 40 on the control panel 36, slidable in a slot 42, sets the
desired position of the hydrocarbon pump 22 relative to the
hydrocarbon/water interface 24. The flow control circuit 38 compares the
signal set by the lever 40 to a signal 41 from the pump unit 22, by means
of a signal comparator 44, and sends the resulting signal to a duty cycle
controller 46 that automatically varies the duty cycle of the solenoid
valve 34 appropriately through cable 45, to control the outward flow of
water 14, while leaving the water pump 26 running in a continuous or near
continuous mode. This provides for a very responsive and automatic water
table depression control as opposed to starting and stopping the water
pump 26. In place of the solenoid valve 34 a motor control valve (not
shown) may be used to proportionately open or close slightly in response
to settings of the control lever 40 and the flow control circuit 38 such
as to maintain the water/hydrocarbon interface level as required.
FIG. 2 shows the hydrocarbon pump unit 22 that is inserted into the well 10
and maintained in position at the hydrocarbon/water interface 24. The pump
unit 22 is cylindrical to conform to the well casing 20 and essentially
comprises a hydrocarbon pump 48 with an intake 50 for drawing in
hydrocarbon liquid 16, a linear probe 52, fixed in relation to the pump
intake 50 for determining the linear location of the hydrocarbon/water
interface 24 relative to the pump intake 50, and an inlet screen 54.
The pump 48 of the unit 22 is conventional, and readily available. Its
purpose is to pump hydrocarbon liquid 16 from atop the water 14 in the
well 10, through a conduit 56, to a tank 58 where the hydrocarbon 16 is
collected for disposal. The tank 58 for collection of hydrocarbon 16
includes a conventional fluid level monitor 60 and a cable 62 for
transmitting a signal indicating that level to a fluid level indicator 64
on the control panel 36, where it can be monitored by the operator.
The probe 52 of the hydrocarbon pump unit 22, which locates the relative
linear location of the interface 24, includes an electrically conductive
member of suitable length 66 arranged to be coaxial with the well 10 and
perpendicular to the hydrocarbon/water interface 24. The conductor 66 is
coated with a non-conductive coating 68 such as the synthetic fluorine
sold under the trademark Teflon. The conductor 66 is connected by a cable
70 to a source of a low frequency electrical signal, such as a low
frequency oscillator 72 and a driver amplifier 74. In effect, the coated
conductor 66 acts like an antenna.
The system also includes a signal detector 76, for measuring the amount of
drive current required to drive the coated conductor 66. The output signal
from the detector 76 depends on how much of the antenna 66 is immersed in
water. This is because the water is relatively conductive and acts as a
shield around the antenna 66. Hydrocarbons, on the other hand, are
relatively non-conductive and therefore do not act as a shield. As more of
the antenna 66 is immersed in the water, the drive current increases. The
drive current in fact is proportional to the extent of immersion of the
antenna 66 below the hydrocarbon/water interface 24. The amplitude of the
drive current is then a continuously varying signal that indicates the
continuous linear position of the pump inlet to the interface. The control
panel 36 has suitable conventional circuitry, including a receiver
amplifier 80, to receive the signal, send it to the signal comparator 44
of the valve control circuit 38 and also display it. For example, in the
control panel 36 shown (see FIG. 3), a series of dual color LED's 82
(light emitting diodes) indicate the level of the interface 24 with
respect to the pump intake 50. Circuitry is provided so that an LED 82 is
activated green to indicate water and red to indicate hydrocarbon.
The pump unit 22 also includes two independent back up point sensors, a
high limit sensor 86 located just under the intake 50 and a low limit
sensor 84 located below the linear probe 52. The sensors 84, 86 are
similarly constructed and utilize the same concept as the linear probe 52
of a low frequency antenna whose signal is changed by the shielding effect
of the water. Each of these sensors 84, 86, however, may be configured as
a horizontal loop of insulated wire as the antenna, thus obtaining its
full signal change within 0.1" of change in the level of the
water/hydrocarbon interface 24 they are monitoring. The back up sensors
84, 86 are connected to control circuitry in the panel 36 to automatically
turn off the hydrocarbon pump 48 when the water/hydrocarbon interface is
above the high limit sensor 86 or below the low limit sensor 84.
Furthermore, the location of the liquid/air interface is also found, with a
conventional liquid level finding system such as floats capacitance,
thermistor beads or optical sensor. In the preferred embodiment, the probe
includes a magnet embedded in a float 90, that activates a number of reed
switches (not shown) placed at incremental heights inside the unit 22. The
signal from these switches is transmitted to the control panel 36, where
it is received and conventional circuitry is used to provide which LED's
82 should be turned off completely to indicate the absence of surrounding
liquid of any type.
Thus, it can be seen that the control panel indicates the location of the
pump intake 50 relative to the hydrocarbon/water interface 24 and also the
depth of the hydrocarbon layer 16. The pump 48 is fixed in its position,
but turned on or off only when an appropriate level of interface 24 exists
or is created by operation of the submersible water pump 26.
Operation of the system shown in FIG. 1 takes place as follows. The pump
and probe unit 22 is lowered into the well 14 until it is at some suitable
position below the the hydrocarbon/water interface 24. When the system is
turned on by switch 92 on control panel 36 the submersible pump 26 will
pump water 14 out until the hydrocarbon/water interface 24 falls below the
hydrocarbon pump intake 50 as shown in the control panel LED's 80: green
for water, red for hydrocarbon, off for the absence of liquid. The
hydrocarbon pump 48 is then turned on by the pump switch 94 on the control
panel 36, as long as there is hydrocarbon 16 available to pump and there
is capacity in a hydrocarbon receiving tank 58. Lights 96 on the control
panel fluid level indicator 64 indicate the general height of hydrocarbon
16 in the tank 58: the lights 96 indicate how many feet from the maximum
level of the tank capacity are left. When the tank 58 reaches its
capacity, of course, the hydrocarbon pump 48 will automatically be shut
off.
The slide control lever 40 on the control panel 36 is used by the operator
to set the desired distance between the pump intake 50 and the
hydrocarbon/water interface 24 as shown by a calibrated scale 98 located
next to the lever 40. The solenoid valve 34 is automatically operated to
let water through conduit 30 if the interface has to be lowered to achieve
the desired relative position, or restricts flow if the level of the
interface has to rise. Ordinarily the operator will set the interface
level 24 well below the pump intake 50 at the initial stages of a clean up
operation, when there may be biological growth at the hydrocarbon/water
interface that could clog the pump or piping. During the final stages of a
clean up operation the pump intake 50 can be set closer to the interface
level 24 (within a fraction of an inch of the pump intake) when it is
necessary to skim off the remaining hydrocarbon.
In alternative systems, the hydrocarbon pump unit 22 may be used in a well
10 without a submersible pump. The pump unit 22 may be simply lowered into
the well, by hand, or mechanically, until the hydrocarbon/water interface
24 is indicated on the control panel 36 as being at the appropriate level
relative to the pump intake 50, and the pump 48 will then be automatically
turned on.
As shown in FIG. 5, for example, in an optional scheme without water
depression, the pump unit 22 is suspended by a cable 99 from a pump lift,
such as an electric winch 100, which is controlled from the control panel
36. Its location in the well 10 is determined by the operation of the
winch 100. The pump unit 22 is raised or lowered until its pump intake 50
is just above the hydrocarbon/water interface 24 in the well 10 as
determined by the linear probe 52 in the pump unit 22.
Furthermore, the interface measurement portion of the hydrocarbon pump unit
probe, while shown as linear, may take the form of a rod or a plate or a
loop of wire. Other embodiments of the invention may occur to those
skilled in the art, and are considered to be within the scope of the
following claims.
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